counterterm

The story

1. Proto-Indo-European*ḱe?
2. Proto-Indo-European*ḱóm
3. Proto-Italic*kom
4. Proto-Italic*kom-
5. Proto-Italic*komteros
6. Proto-Italic*komterād
7. Latincontrā
8. Old Frenchcontre-
9. Anglo-Normancountre-
10. Middle Englishcounter-
11. Englishcounter-
12. Proto-Indo-European*terh₂-?
13. Proto-Indo-European*ter-?
14. Proto-Indo-European*térmn̥
15. Proto-Italic*termn̥
16. Proto-Italic*term(e)nos
17. Latinterminus
18. Old Frenchterme
19. Middle Englishterme
20. Englishterm
21. English todaycounterterm

From counter- + term.